A printer based on the so called ink jet process which prints on paper, cloth, film and the like by jetting liquid or solid ink from a nozzle, slit or porous film has been intensely examined for its miniature size, inexpensiveness, quietness and the like. Particularly as a black single-color printer, a printer which prints well on so called plain paper such as reporting pad paper and copy sheets is also desired.
For an ink used in an ink jet printer, the following five features are required. One is being capable of obtaining a uniform image of high density and high resolution free of bleeding and fog. The second is always being good in jettability and jetting stability, free of blindings caused by ink drying at the tip of the nozzle. The third is having quick drying property on a paper. The fourth is having fastness of image, and the fifth is having long-term preservation stability.
To satisfy these requirement, various additives and water soluble organic solvents are being examined. For example, in Japanese examined patent publication Sho. 62-11781, the use of interfacial active agent is described. In Japanese unexamined patent publications Sho. 62-89776 and Hei. 1-25789, the use of block copolymer consisting of ethylene oxide and propylene oxide is described.
In conventionally proposed inks, however, one having all of above described five features has not been obtained. On the other hand, although ink jet printers capable of producing full-color images are also desired, when printing on plain paper, they suffer from poor drying property, disturbance of high speed printer output, and mixture of different color tones, which leads to poor image rendering. Therefore, it is necessary to use particular surface treated dedicated paper, which results in high cost and difficulty in popularization of it as a general purpose printer.